Feedback modulation of exhaust gases in internal combustion engines

ABSTRACT

A system for modulation of the amplitude of engine exhaust feedback to the engine induction system during engine operation. The modulation system includes means for varying the amplitude of exhaust feedback in periodic manner at a frequency which is substantially constant or which may vary as a function of an engine operating parameter. The amplitude may vary as a step function between predetermined levels or continuously and may have a duty cycle (length of time at a predetermined level) which varies as a function of an engine operating parameter, e.g. exhaust manifold temperature. The modulation envelope is controlled by a modulator circuit controlling a valve position in the feedback path. The frequency of modulation is controlled by a divider or multiplier type circuit coupled between a pulse source e.g. the distributor and the modulator circuit.



1. In an internal combuStion engine having an intake manifold, and a feedback path coupled between said exhaust manifold and said intake manifold for recirculating exhaust gases from said exhaust manifold to said intake manifold; means for modulating the rate of flow of exhaust in said feedback path, said means comprising: timing means including a pulse source for generating first control signals; modulator circuit means including a multivibrator circuit responsive to said first control signals for providing valve control signals, and, valve means disposed in said feedback path and responsive to said valve control signals for modulating the rate of flow of exhaust gases in said feedback path.
 2. An internal combustion engine according to claim 1 wherein said first control signals are a function of engine speed.
 3. Process for operating an internal combustion engine in a manner to reduce pollutants ejected into the atmosphere which comprises recycling of exhaust gases while modulating the rate of flow of said exhaust gases cyclically during operation of said engine.
 4. Process of claim 3 wherein said cyclic variation is over a period of time exceeding about 100 milliseconds.
 5. In a motor vehicle powered by an internal combustion engine: first means for reducing emission of pollutants by said engine; second means coupled to said first means for detecting the level of a pollutant in the ambient air surrounding said vehicle and actuating said first means when said level of a pollutant exceeds a predetermined level.
 6. The invention according to claim 5 wherein said second means is positioned on said vehicle.
 7. The invention according to claim 5 wherein said first means comprises a feedback path including recirculation control valve means.
 8. In an internal combustion engine having a feedback path for recirculating engine exhaust; means including electrically controlled valve means disposed in said feedback path and further including a modulator circuit coupled to said electrically controlled valve means for modulating said recirculating engine exhaust between predetermined levels in a cyclical manner.
 9. The invention according to claim 8 wherein said predetermined levels are 0 and 100 percent.
 10. The invention according to claim 8 wherein said cyclical variation is a function of engine exhaust temperature.
 11. The invention according to claim 8 wherein said modulation varies as a function of an engine operating parameter.
 12. In combination in a motor vehicle having an internal combustion engine including ignition distributor means, intake manifold, exhaust manifold, and an exhaust passage coupled to said exhaust manifold for exhaust gas flow from said exhaust manifold to the atmosphere, the combination comprising: a divider circuit responsive to pulses flowing in said ignition distributor means; utilization means disposed in said internal combustion engine; and, a modulator circuit responsive to the output of said divider circuit for providing control signals for controlling said utilization means.
 13. The combination of claim 12 wherein said modulator circuit comprises a multivibrator circuit.
 14. The combination of claim 12 wherein said modulator circuit includes means responsive to an engine operating parameter for varying the characteristics of said control signals.
 15. In the method of operating an internal combustion engine, the steps of providing an exhaust flow path for recycling exhaust flow from said engine, and applying periodic modulation to the exhaust flow in said exhaust flow path to control the peak flame temperature.
 16. In the method according to claim 15, said step of applying periodic modulation comprising applying said modulation as a function of an engine operating parameter.
 17. In the method according to claim 15, the additional step of varying the duty cycle of said periodic modulation.
 18. In combination in an internal combustion engine having an intake maNifold, and a feedback path coupled between said exhaust manifold and said intake manifold for recirculating exhaust gases from said exhaust manifold to said intake manifold; electrically controlled valve means disposed in said feedback path for modulating the rate of flow of exhaust gases in said feedback path; a modulator circuit coupled to said electrically controlled valve means; and means coupled to said modulator circuit for causing modulation of said modulator circuit to vary as a function of an engine operating parameter. 